Circuit breaker



Nov. 14, 1950 w. T. ALLEN 2,529,754

CIRCUIT BREAKER Original Filed Dec. 24, 1942 Jg [giggly III I PatentedNov. 14, 1950 CIRCUIT BREAKER Wallace'l. Allen, Dearborn, Mich assignorto Square 1) Company, Detroit, Mich., a corporation of Michigan Originalapplication December 24, 1942, Serial No.

Divided and this application October 21, 1949, Serial No. 122,629

6 Ciaims. 1

This invention relates to current responsive thermostatic elements, andmore particularly to automatic electric circuit controlling devicesemploying current responsive thermostatic tripping elements.

An object of the present invention is to provide an improved trippingmeans for an automatic electric circuit breaker.

Another object of this invention is to provide in an automatic electriccircuit breaker thermostatic means for eiiecting improved operation ofthe circuit breaker on the occurrence of heavy current overloads.

Another object of this invention is to provide an automatic electriccircuit breaker employing a current responsive tripping member with apart thereof being thermally effected on the occurrence of heavy currentoverloads, and the remainder thereof being substantially thermallyunaffected except on sustained overioads.

Another object of this invention is to provide a thermal trip means foran automatic electric circuit breaker comprising a bimetallic elementcarrying a non-bimetallic latching element movable relative to thebimetallic element under a sustained current overload.

Other objects and features of this invention will be readily apparent tothose skilled in the art from the following specification and theappended drawing illustrating certain preferred embodiments of theinvention in which:

Figure 1 is a partial front elevational view of an automatic electriccircuit breaker utilizing the tripping means according to the presentinvention and in which portions are cut away to show internal parts.

Figure 2 is a vertical sectional line taken on line IIII of Figure 1.

This application is a division of application Serial No. 470,044 in thename of Wallace T. Allen dated December 24, 1942, and which has becomePatent No. 2,503.591, issued May 23, 1950.

Referring to the drawings, Figures 1 and 2 illustrate a circuit breakermechanism specifically disclosed and claimed in the patents of John G.Jackson, No. 2,096,545 issued October 19, 1937, and No. 2,132,625 issuedOctober 11, 1938, and both entitled Circuit Breakers, and with 2.current responsive thermostatic tripping element according to thepresent invention. These figures illustrate one form of circuit breakerin which the tripping element, according to the present invention, maybe employed although it is obvious that the tripping element issusceptible of use 2 apparatus in which a thermostatic latching memberis employed.

The circuit breaker illustrated embodies a metallic mounting plate Iwhich may be the back wall of an outer enclosing box against which ismounted an insulating base 2. Generally centrally inthis base is mounteda stationary contact plate 3, as by means of a stud and carryingstationary contacts 5 adapted to cooperate with movable contacts 5 onthe ends of contact blade 1. Upon ledges at the ends of the base 2 arerigidly supported connectors 8 as by means of spun over portions ofmetallic inserts 9 which also receive terminal studs H. To the interiorend of each of the connectors 8 is rigidlysecured one end of abimetallic member 2'! as by means ofan adjusting means generallydesignated at 53.

As shown in Figur 2, the tripping member comprises a bimetallic member 2to which is rigidly securedby'welding at a single weld pointv thenon-bimetallic or thermally non-active element 28 havingthe end thereofbent as at 29 to provide a latch for engagement with a tip iii of thecontact blade I. The single point of Weld is indicated in Figure 2 inconventional manner by a small a: at the juncture between the joinedelements 2'! and 28.

A compression spring 18 biases the movable contact if carried by theblade 1, against the stationary contact 5, and biases the tip [0 of theblade against the latch 29 of the non-bimetallic member 28. A U-shapedmember I9 having legs of dissimilar length is guided by formations inthe base for rectilinear movement at right angles thereto. The longerleg of the member [9 is slotted to receive the blade I, and the blade atits top edge is provided with a notch 2| received within the top edge ofthe slot. A second notch 22 is provided in the front edge of the blade,and is adapted to engage a shorter leg of the member 19 to serve as astop for the blade upon rotation as hereinafter described. An operatinghandle 23 pivotally mounted on a shaft 24 has an interior cam surfacewhich effects rectilinear movement T of the member H, which cam surfaceincludes a flat staple portion 25 and a resetting tip 26.

The blade 1 of Figure 2 is in the normal on position. To move the partsto the manual off .position, the handle is rotated counterclockwiseuntil the flat surface 25 engages the top surface of the member [9 whichproduces a stable position in which the member l9 has been moved towardthe bottom of the base and has separated the movable contact at the endof the associated in any type of circuit breaker or in any other 55blade 1 from its cooperating stationary contact 5.

In the automatic operation of th breaker, this invention provides for aquicker tripping of the switching parts on the occurrence of shortcircuits and heavy current overloads than previously obtained in circuitbreakers, with consequent added protection to the circuit breaker parts,and to the circuit controlled thereby. This feature of more rapidtripping is effected in a manner now to be described;

The breaker is so constructed that on moderate overload the bimetallicelement 21, a substantial portion of which is in series circuit with thecontacts, is heated by the current, this heat being transmitted to thenon-series portion by conduction whereby this non-series portion flexes.This fiexure causes the latch end 29 of the nonactive element 28 to movetoward its engagement with the blade I; that is, as the non-series partof bimetal 21 is bowed upon a rise in temperature, element 28 willassume a position tangent to the arc of bimetal 21 at point of juncturea: to move latch 29 toward tip Ill of blade I to tend to oppose thereleasing movement of element '2'! and to tend to maintain the latch 29in engagement with the tip I0 until the attainment of the rated currentfor the device. After the attainment of a predetermined degree ofoverload, the bimetal 21 will flex sufficiently to move the latch 29 offof the tip I0 of the contact blade I, whereupon this blade rotates in acounterclockwise direction about the engagement of the notch 2| with themember 19, and under the bias of spring I8 into the contacts disengagedposition, thus interrupting the circuit through the breaker mechanism.Upon heavy current overload, the non-series portion is not heated enoughto flex as the breaker trips quickly due to flexing of the currentcarrying portion of bimetal 2'! by the heat generated by the currentflow therethrough. To reset the parts after an automatic release, thehandle is rotated past the off position until the resetting tip 26 is onthe top surface ofmember [9, in which position the contact blade I willhave engaged the bottom of the arc chamber and moved back into positionto engage this latch 29. If the bimetal 21 has cooled sufiiciently toassume its normal position, releasing the handle will then place theparts in the normal oif position,

whereupon clockwise rotation of the handle will P again permit the partsto assume the positions shown in Figure 2.

The tendency of the tripping element to maintain engagement with acontact blade on moderate overload permits the employment of a lesseroverlap between latch and blade than ordinarily required to obtain thedesired rating or calibration. With the use of a lesser overlap, it isobvious that on the occurrence of a heavy overload, the latching meanshaving a lesser distance to move to efiect release of the blade 1, willeffect tripping in a lesser time. Lessening the trip time on theoccurrence of heavy overloads is definitely a desirable feature for itlessens the possibility of damage to the circuit breaker parts by theheavy overload current.

It is evident then that a circuit breaker, by employing a trippingmember of a type described herein in which a portion opposes release ofthe contact blade on the occurrence of a moderate overload, will retainits given rating and will not trip out too quickly on moderate overloadsand yet will effect a materially faster release of the switching :partson the occurrence of a short circuit or heavy overload, and thereforeresults in 4 better protection to the circuit breaker and its associatedcircuit.

While a certain preferred embodiment of the invention has :beenspecifically disclosed, it is understood that the invention is notlimited thereto, and many variations will be readily apparent to thoseskilled in the art and the invention is to be given its broadestpossible interpretation within the terms of the following claims.

What is claimed is:

1. An automatic circuit breaker, separable contacts, a switching memberfor effecting separation of the saidcontacts to open the circuit throughthe breaker, a thermostatic member for initiating operation of saidswitching member, a flexible lead interconnecting said thermostaticmember and said switching member, said flexible lead being secured tosaid thermostatic member intermediate the ends thereof whereby but aportion of said thermostatic member is in series circuit with saidcontacts, a thermally inactive member secured to that portion of saidthermostatic member which is not in series circuit with said contacts,said thermally inactive member being attached to said thermostaticmember only near one extremity of said thermally inactive member andhaving a latching surface near the opposite extremity of said thermallyinactive member engageable with said switching member, said seriescircuit portion of said thermostatic member, being movable towardreleasing position on the occurrence of moderate overload current, atleast that portion of said thermally inactive member having the latchingsurface also being movable relative to said thermostatic member on saidoccurrence of a moderate overload current so as to tend to maintain saidlatching surface in engagement with said swit hing member.

2. In an automatic electric circuit breaker, a stationary contact, amovable contact, a switching member for moving said movable contact intoand out of engagement with said stationary contact, a manual member formoving said switching member to perform the switching operation, andmeans for causing automatic separation of said contacts, said meanscomprising a bimetallic element and a member carried thereby, saidmember being attached only near one of its ends to said bimetallicelement and having a latching portion near its unattached end engageablewith said switching member to normally maintain it in position foroperation by said manual member, said bimetallic element on theoccurrence of a predetermined overload current flexing to move saidmember carried thereby to a position tangent to the are formed by saidbimetallic element whereby said latching portion is moved relative tosaid bimetallic element so as to tend to maintain engagement with saidswitching memberl 3. In an automatic electric circuit breaker, astationary contact, a movable contact, a switching member for movingsaid movable contact into and out of engagement with said stationarycontact, a manual member for moving said said switching member tonormally maintain it in position for operation by said manual member,said bimetallic element on the occurrence of a predetermined overloadcurrent flexing in a first direction to move said thermally inactiveelement to a position tangent to the are formed by said bimetallicelement to move said latching portion relative to said bimetallicelement in a direction to tend to maintain engagement with saidswitching member.

4. In an automatic electric circuit breaker, separable contactscontrolling the flow of current through the breaker, and thermallyresponsive means for initiating operation of said contacts to separatedposition in response to the passing of overload currents through thebreaker, said means including a bimetallic member having fixed and freeends, an electrical conductor connected to said bimetallic memberintermediate its ends and to one of said contacts thereby placing onlythe part of said bimetallic member between its fixed end and the pointof connection of said conductor in series circuit with the contacts soas to be traversed by the current passing through the breaker wherebysaid part of the bimetallic member is directly heated by current flowtherethrough, a thermally unaffected latch member, means joining saidlatch member only near one extremity thereof to the non-series portionof said bimetallic member the latch on said latching member being nearthe extremity thereof opposite that joined to said bimetallic member,the bimetallic member being quickly heated upon occurrence of a shortcircuit current to rapidly move said latch member to unlatched position,the non-series portion of said bimetallic member being heated byconduction from said series portion upon the occurrence of a moderateoverload and flexing in a direction to move said latching portion towardlatched position.

5. In an automatic electric circuit breaker, separable contactscontrolling the flow of current through the breaker, and thermallyresponsive means for initiating operation of said contacts to separatedposition in response to the passage of overload currents through thebreaker, said means including a bimetallic member having fixed and freeends, an electrical conductor connected to said bimetallic memberintermediate its ends and to said contacts thereby placing only the partof said bimetallic member between its fixed end and the point ofconnection of said conductor in series circuit with the contacts so asto be traversed by the current passing through the breaker whereby saidpart of the bimetallic member is directly heated by current flowtherethrough, a thermally non-responsive latching member, meansconnecting the latching member to the non-series portion of saidbimetallic member at a single point remote from the current carryingportion thereof, the latch portion of said latching member being remotefrom the point at which said latching member is connected to saidbimetallic member, the bimetallic member being rapidly heated upon theoccurrence of a substantial overload to quickly move the latch portionof said latching member toward unlatched position, the non-seriesportion of said bimetallic member being heated by conduction from saidseries portion upon occurrence of a moderate overload and flexingthereby to move the latch portion of said latching member away from thebimetallic member to effect an overall unlatching movement which is adifferential of the movements of the bimetallic member and the latchportion of the latching member.

6. In an automatic circuit breaker, separable contacts controlling theflow of current through the breaker, thermally responsive means forinitiating the opening operation of said contacts upon the passage ofoverload current through the breaker, said means including a bimetallicmember having fixed and free ends, means for heating at least thatportion of said bimetallic member adjacent .its fixed end, a rigid latchmember, means connecting one extremity of said latch member to the freeend of said bimetallic member, said latch member having a latchingportion near the extremity of said latch member opposite to that affixedto said bimetallic member, the latching portion of said latching memberbeing movable relative to said bimetallic member upon the occurrence ofpredetermined thermal conditions in the circuit breaker.

WALLACE T. ALLEN.

REFERENCES CITED UNITED STATES PATENTS Name Date Lindstrom Feb. 23, 1937Number Certificate of Correction Patent No. 2,529,754 November 14, 1950WALLACE T. ALLEN It is hereby certified that error appears in theprinted specification of the above numbered patent requiring correctionas follows:

Column 1, line 42, for Patent No. 2,503,591 read Patent N 0. 2,508,591;

and that the said Letters Patent should be read as corrected above, sothat the same may conform to the record of the'case in the PatentOffice. Signed and sealed this 16th day of January, A. D. 1951.

[smnl THOMAS F. MURPHY,

Assistant Commissioner of Patents.

Certificate of Correction November 14, 1950 Patent No. 2,529,754

WALLACE T. ALLEN It is hereby certified that error appears in theprinted s on as follows:

above numbered patent requiring correct-1 Column 1, line 42, for PatentNo. 2,503,591 read Patent N 0. 2,508,591; e, so that the and that thesaid Letters Patent should be read as corrected abov same may conform tothe record of the case in the Patent Office.

Signed and sealed this 16th day of January, A. D. 1951.

pecification of the [SEALl THOMAS F. MURPHY,

Assistant Commissioner of Patents.

